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20 January 2013

What a Komodo dragon can teach us about energy balance

Credit: San Diego Zoo

Try telling a Komodo dragon that physical activity doesn't matter and that all one needs to do to lose weight is eat a diet lower in carbohydrates.

Meet Sunny, the obese Komodo dragon. Her San Diego Zoo keepers have put her on a strict diet based on her animal energy and metabolic requirements. She eats only mice, rats, and ground turkey mixed with vitamins and calcium. Yet, it's not enough to keep Sunny from steadily gaining weight. When in captivity, dragons are prone to obesity because of their mainly sedentary lifestyle. They do little else than sleep, bask in the sun or shade, and eat breakfast or supper.

In their native habitat of Indonesian islands, Komodo dragons are extremely active. They travel up to 10 kilometers a day, run up to 13 miles per hour, swim several kilometers from island to island, then dig or climb as they hunt. Once they capture their prey, they can eat as much as 80 percent of their body weight in a single meal. That energy they will serve to store for often days or weeks.

When I asked senior zookeeper Ken Morgan what he was doing to help get Sunny moving and losing weight, he replied that they were trying a series of enrichment programs. But getting a 200-pound dragon to do any activity at all is no easy task, he said. It takes some creativity. One enrichment program Morgan has used involves burying a ball with a dead mouse inside. Sunny picks up the scent, spends some time searching for it, then digs around before finally discovering the treasure. It's activity accomplished. These games can help Sunny burn more calories to keep weight off.

Credit: Jordan A. Veasley and Giorgio Guerra

Similar efforts are going on at other zoos. At Woodland Park Zoo, Jordan Veasley and Giorgio Guerra of the University of Washington decided to compare the amount of activity produced by some of the most popular enrichment programs on two Komodo dragons -- Loki and Selat. They found that the most successful program was the "scent trail." This treasure hunt of sorts involves using meat juice to create a simple, yet intricate path around a dragon's enclosure that would lead to a dead mouse. When the dragons performed the activity, the researchers found that it displaced a lot of the time that would normally be used for simply resting. Instead, the dragons swam, dug, climbed and honed the skills of these endangered animals for greater possibility of successful release into the wild. The researchers also noted that the Komodo dragons performing the activities had greater levels of "excitement and joy."

Credit: Jordan A Veasley and Giorgio Guerra.

Komodo dragons, of course, aren't the only animals in the zoo that are prone to obesity. Proper diet and environment play important roles, to be sure. But most zoos recognize the critical role of enrichment activities as part of an overall approach to help their animals keep weight off. I mainly focus on the example of Sunny, because it so nicely serves as a model to illustrate the why the energy balance paradigm isn't going to go away anytime soon. As a way to battle obesity, we humans might also learn a thing or two from the zookeepers.

Have you read about American zoo gorillas and how they are dying on a vegan sugar and starch diet?zoo keepers then switched them to a diet more closely related to their original habitats, and viola, now they are eating twice as many calories and losing weight.

Teech, I've written previously about the diets of gorilla, which consists mainly of leaves. Interestingly, most of their energy comes from short-chain fatty acids produced from fermentation of the leaves in their intestines. In contrast, chimps eat more of a fruit/meat diet. You can read about it here: http://evolvinghealthscience.blogspot.com/2011/09/what-chimpanzee-predatory-behavior-can.html

I always enjoy your posts. As an exercise physiologist, I love this one. Trying to get people to understand how many calories we don't burn due to our sedentary lifestyle is difficult. Great example. I think intermittent fasting also mimics the way we evolved.

About Me

I'm a science and health writer based in the Gilbert, Ariz., specializing in topics such as biology, health, food science, nutrition, and medicine. My background is in science communications with a master's of science degree in human nutrition and a bachelor's of arts degree in English. I've written for a variety of publications including Scientific American, Outside Online, the American Society for Nutrition's Nutrition Notes Daily, and the Institute of Food Technologists' Food Technology. I'm an active member of several respected organizations including the National Association of Science Writers and the American Association for the Advancement of Science. I'm also interested in wildlife conservation and am a member of the National Audubon Society and the American Society of Naturalists.